An externally valved shunt for a cardiopulmonary bypass pump is disclosed in U.S. Pat. No. 4,553,532, dated Nov. 19, 1985, wherein a suspended roller-like valve element is positioned at the inlet and outlet of a tubing shunt for controlling the flow of blood through the compressible tubing shunt mounted in the compression chamber of a pulsatile flow pump.
While the roller-like valve elements have performed their intended function, the external plate valves of the present invention are an improvement over the roller-like valves disclosed in the above-mentioned patent in that the plate valves of the present invention are not fixedly connected to the compression chamber or housing of the pump so that the distance between the inlet and outlet valves can be adjusted, thereby allowing adjustment of stroke volume to fit the needs of small and large patients, and also to control the degree of hemolysis and lactic acidosis present in the patient.